The microwave heating and reconstitution of food products for consumption by the application of microwave energy is well known. Microwave heating occurs by the excitation of water molecules within the body of the food. This manner of heating is different from conventional oven heating, which involves heating from the exterior of the food product. While both methods are effective in heating food products, nevertheless one significant difference exists, in that microwave cooking does not produce browning or crisping of the exterior of the product.
This difference is of no significance with some food products but is of considerable significance with other products, such as those having a pastry shell, for example, a frozen pizza. Frozen pizzas reconstituted in a microwave oven tend to be soggy and lack crispness in the pastry whereas such crispness is attainable by conventional oven heating.
It has been suggested to supplement microwave cooking to achieve crispness of the type found with conventional oven heating to use a metallized sheet in contact with the pie crust. The concept is that the microwave energy is concentrated in the metallized sheet, thereby heating the metal layer, which in turn heats the food stuff by conduction from the heated metal layer, hoping thereby to produce a crispness in the pie crust.
While some success can be achieved in this regard, it has been found that the heating is uneven and, if the center portions of the pie crust are sufficiently crisped, the peripheral regions are overcooked and burned. If the peripheral regions are sufficiently crisp, then the inner regions remain insufficiently crisp.